1. Field of the Invention
This invention relates to polyester adhesive compositions and their use in laminated structures, particularly photographic elements and processes to obtain a desirable combination of properties. In particular, this invention relates to heat-activatable, water-dispersible adhesive compositions capable of bonding hydrophilic surfaces to hydrophobic surfaces in photographic materials. A preferred embodiment of this invention is the use of certain bisamide group-containing polyester adhesives which contain an anionic iminodisulfonyl group in image transfer film units.
2. Description of the Prior Art
Arcesi et al., in U.S. Pat. No. 3,929,489 issued Dec. 30, 1975, describe water-insoluble light-sensitive polyesters comprising a diol component which may include 1,4-bis(2-hydroxyethoxy)cyclohexane; and a diacid component comprising from 2 to 45 mole percent of ionic iminodisulfonyl units, from 55 to 98 mole percent of light-sensitive crosslinkable units and up to 43 mole percent of other units derived from other diacids such as aliphatic dicarboxylic acids. These polyesters are soluble in organic solvents and aqueous alcoholic alkaline developers, and are used in photographic elements such as lithographic printing plates and photoresists. These water-insoluble polyesters have no disclosed use as adhesives in silver halide photographic materials.
Caldwell et al., in U.S. Pat. No. 3,546,180 issued Dec. 8, 1970, describe dyeable polyesters for shaped articles such as fibers and films. These polyesters comprise a diol component which may include cyclic glycols; and a diacid component comprising from 1 to 15 mole percent of ionic iminodisulfonyl units and other diacids which may include aliphatic dicarboxylic acids. Further, the polyesters of Caldwell et al may have additional utility as adhesives when small amounts of water-insoluble crosslinked polymers are added. However, like other water-insoluble adhesives known in the art, these polyesters must be coated with organic solvents. Organic solvents are substantially more costly to use than aqueous solutions. Further, the disposal of organic solvents is burdensome, since, if untreated, organic solvents can be ecologically objectionable.
Noonan, U.S. Pat. No. 4,150,217 issued Apr. 17, 1979, describes a water-soluble polyester adhesive comprising a diol component which may include 1,4-bis(2-hydroxyethoxy)cyclohexane; and a diacid component comprising from 15 to 35 mole percent of ionic iminodisulfonyl units, and from 65 to 85 mole percent of units derived from other dicarboxylic acids, which may include aliphatic dicarboxylic acids and light-sensitive ethylenically unsaturated dicarboxylic acids. However, these water-soluble polyester adhesives exhibit blocking problems when machine coated onto spool-would materials. Further, high humidity conditions and use of an aqueous processing composition with a photographic element in an image transfer unit deleteriously affect the integrity of seals formed from the adhesive in the photographic element or image transfer film unit.
There is a need in the photographic arts for a water-dispersible, heat-activatable adhesive which can be easily and inexpensively coated from water as a stable aqueous dispersion, but which dries and coalesces to a water-insoluble adhesive film which is insensitive to humidity variations, unaffected by the presence of aqueous processing composition, and free from the blocking problems encountered with machine coatings of water-soluble polyester adhesives. Further, the dried coating when sealed, should exhibit acceptable adhesive qualities.